Predictive dead time controller for GaN‐based boost converters

Abstract

A dynamic dead time controller is presented, specifically intended to operate in synchronous boost converters based on GaN field-effect transistor switches. These transistors have a reduced stored charge with respect to silicon metal-oxide-semiconductor field-effect transistors with similar breakdown voltage and series resistance, and can operate at higher frequencies with reduced switching losses. On the other hand, the voltage drop in reverse conduction is typically more than doubled with respect to silicon devices resulting in relevant power losses during the free-wheeling phases. Therefore, dynamic control of dead time can be profitably applied even in converters operating in the tens of volts range. The device presented in this study controls the switching delays taking into account both variations of the fall/rise times and of the turn-off/on delays, in order to keep dead time within a range of a few nanoseconds above its minimum value. A discrete-component prototype was designed, built in a synchronous boost converter and extensively tested at 1-2MHz switching frequency, in a range of operating parameters corresponding to significant variations of the switching times (currents in the 1-6A range, output voltage up to 50V). The prototype demonstrated the capability to match dead time to actual operating conditions with a smooth and fast transient response

10 MHz boost converter with subthreshold voltage startup and predictive dead‐time techniques for energy‐harvesting systems

“…Moreover, the dead-time control is implemented in the boost converter and has high resolution to fully improve efficiency under different load conditions. Compared to [24], the higher efficiency improvement and dead-time resolution is obtained in proposed scheme. The efficiency improvement of 3% in [32] is compared with the case where the fixed dead time is ∼20.48 ns.…”

“…The efficiency improvement of 3% in [32] is compared with the case where the fixed dead time is ∼20.48 ns. Compared with the CMOS topology, the higher efficiency can be achieved easily because of the GaN‐based converter in [24, 32]. The dead‐time resolution in [32] is close to ours, however, its predictive approach only intended to operate in GaN‐based converter.…”

“…However, the body diode conduction loss, which happens in the dead time, is one of the critical losses in the multi-MHz (≥10 MHz) switching frequency converter. Recently, several dead-time control concepts are put forward [21][22][23][24]. In the design of [21], one-step delay dynamic dead-time controller can rapidly track the change of loads.…”

“…The complicated searching algorithm limits its application for the simple converter. Moreover, the resolution of predictive techniques reported in [24] is restricted by its feedback closed-loop adjustment mechanism. However, this predictive approach only intended to operate in GaN switches based converter.…”

Tracking Deadtime Algorithm for GaN DC/DC Converter

“…One option is to measure the efficiency depending on the converter power and create a look-up map that determines the optimum deadtime for the control circuit [7]. The other option is to add a specific analogue circuit which measures the voltage drop at reverse conduction as a feedback for the control circuit adjusting the deadtime [8].…”